I have below lambda expression for select list of my model.
Note: state variable can be True, False or NULL.
var list = APPEntites.Submited_Files
.Where(r => r.Category == id.Trim() && r.approved == (bool?) state)
.OrderByDescending(r => r.Date_Created)
.ToList();
I have an issue with selecting. If I pass this STATE variable with Null, it will return 0 list items, but if I use null, it will return the rows correctly. I want to know the reason for this issue.
Note: this code was working perfectly before.
Thank you all.
Restarting Visual studio solved the issue.Strange!!.
var list = APPEntites.Submited_Files
.Where(r => r.Category == id.Trim() && r.approved == state)
.OrderByDescending(r => r.Date_Created)
.ToList();
Related
What is wrong in this query? It's about 2 entities that can be logically deleted by inserting a delete date. So I must be sure I get a single Entity with is collection of SubEntities. All with DateDelete not null.
return DbContext.Entity
.AsNoTracking()
.Include(y => y.SubEntities.Select(sb => sb.DateDelete == null))
.Single(y => y.Name == entityName && y.DateDelete == null);
On runtime I get an exception
The Include path expression must refer to a navigation property
defined on the type. Use dotted paths for reference navigation
properties and the Select operator for collection navigation
properties. Parameter name: path
I also tried this with same error
return DbContext.Entity
.AsNoTracking()
.Include(y => y.SubEntities.Where(sb => sb.DateDelete == null))
.Single(y => y.Name == entityName && y.DateDelete == null);
After my own investigation I found it is impossible to filter on .Include() but there are workarounds by using .Select() method or the filter library.
Workaround 1
return DbContext.Entity
.AsNoTracking()
.Where(e => e.DateDelete == null)
.Select(e => new
{
e.Id,
e.Property,
e.DateDelete,
SubEntities = e.SubEntities.Where(se => se.DateDelete == null)
})
.ToList();
Workaround 2
The solution given by Gert Arnold here with EntityFramework.DynamicFilters. This workaround has some limitation. Read the documentation.
I am fairly new to Linq and I am starting to try and filter lists and IEnumerable content without using foreach loops. In this case I want to retreive a nested property if it meets a given criteria.
Here is what I have so far:
IEnumerable<GroupTourData> test =
web_service_item.TourInstances
.Where(x => x.Availability.Where(a => a.Price > 0 && a.Grade == string.Empty)
.Count() > 0);
What I want to achieve here is an IEnumerable list of all of the prices in the matching criteria. I though this would be obtainable by adding .SelectMany(a.Price) to the end of this statement but that seems to error out in Visual Studio.
Any help or pointers would be greatly appreciated.
ok seems as this solves the issue:
if you just want the prices? then you just had your SelectMany in the wrong position:
web_service_item
.TourInstances
.SelectMany(ti => ti.Availability)
.Where(a => a.Price > 0 && a.Grade == string.Empty)
.Select(a => a.Price);
Depending on your data schema and tables... Have you tried including your sub-entities using Include?
IEnumerable<GroupTourData> test = web_service_item
.TourInstances
.Include("Availability")
.Where(x => x
.Availability
.Any(a => a.Price > 0 && a.Grade == string.Empty)
);
another kinda newbie question I guess. I have EF setup and now I want to select some records based on a filter. I have SomeClass with 4 items (all strings to keep things simple, lets call them string1, string2, and so on). Now, in a post I send the filter in an instance of SomeClass, but maybe not all properties are filled in.
So you might end up with string1="something", string2="bla" and string4="bla2". So string 3 = null. Now, how do I setup the query? If i try something like:
var dataset = entities.mydatabase
.Where(x => x.string1 == someclass.string1 && x.string2 == someclass.string2 && x.string3 == someclass.string3 && x.string4 == someclass.string4)
.Select(x => new { x.string1, x.string2, x.string3, x.string4}).ToList();
... I get no results, because string3=null. I could do something with checking all parameters and see if they're set and create the query based on that, but there must be something more elegant than that.
Anyone?
Thanks!
Ronald
The following will return all rows where the someclass.string is null OR equals to x.string.
var dataset = entities.mydatabase
.Where(x => someclass.string1 == null || x.string1 == someclass.string1)
.Where(x => someclass.string2 == null || x.string2 == someclass.string2)
.Where(x => someclass.string3 == null || x.string3 == someclass.string3)
.Where(x => someclass.string4 == null || x.string4 == someclass.string4)
.Select(x => new { x.string1, x.string2, x.string3, x.string4}).ToList();
I try to change that query to QueryOver<> to be able to do the Distinct operation yet inside the (generated sql) query
var result = (from x in Session.Query<Events>()
join o in Session.Query<Receivers>() on x.ID equals o.ID
where x.Owner.ID == 1 //the user is the owner of that Event (not null)
||
x.EVType.ID == 123 //(not null)
||
x.Receivers.Count(y => y.User.ID == 1) > 0 //the user is one of the Event Receivers
select x.StartDate)
.Distinct();
I tried something like that
Events x = null;
List<Receivers> t = null;
var result = Session.QueryOver<Events>(() => x)
.JoinAlias(() => x.Receivers, () => t)
.Where(() => x.Owner.ID == 1
||
x.EVType.ID == 123
||
t.Count(y => y.User.ID == 1) > 0)
.TransformUsing(Transformers.DistinctRootEntity)
.Select(a => a.StartDate)
.List();
but then I got the Value can not be null. Parameter name: source exception. Any ideas how can I fix that query ?
edit
thanks to the xanatos' answer, the final SQL query is correct (I used his 2nd approach):
SELECT distinct this_.StartDate as y0_
FROM Events this_
WHERE
(
this_.UserID = ?
or
this_.EventTypeID = ?
or
exists (SELECT this_0_.ID as y0_
FROM Receivers this_0_
WHERE this_0_.UserID = ?)
)
"In QueryOver, aliases are assigned using an empty variable. The variable can be declared anywhere (but should be empty/default at runtime). The compiler can then check the syntax against the variable is used correctly, but at runtime the variable is not evaluated (it's just used as a placeholder for the alias)." http://nhibernate.info/blog/2009/12/17/queryover-in-nh-3-0.html
Setting List<Receivers> t to empty collection as you did (as you have mentioned in comments) means that you check is event id in local empty collection - doesn't have sense at all.
You can try do your query with subquery (should work but i'm not sure, I wrote it without testing, "by hand"):
Receivers receiversSubQueryAlias = null;
var subquery = session.QueryOver<Events>()
.JoinQueryOver<Receivers>(x => x.Receivers, () => receiversSubqueryAlias, JoinType.Inner)
.Where(()=> receiversSubQueryAlias.UserId == 1)
.Select(x => x.Id)
.TransformUsing(Transformers.DistinctRootEntity);
Events eventsAlias = null;
var mainQueryResults = session.QueryOver<Events>(() => eventsAilas)
.Where(Restrictions.Disjunction()
.Add(() => eventAlias.OwnerId == 1)
.Add(() => eventAlias.EVType.Id == 123)
.Add(Subqueries.WhereProperty<Events>(() => eventAlias.Id).In(subquery))
).Select(x => x.StartDate)
.TransformUsing(Transformers.DistinctRootEntity)
.List();
As written by #fex, you can't simply do a new List<Receivers>. The problem is that you can't mix QueryOver with "LINQ" (the t.Count(...) part). The QueryOver "parser" tries to execute "locally" the t.Count(...) instead of executing it in SQL.
As written by someone else, TransformUsing(Transformers.DistinctRootEntity) is client-side. If you want to do a DISTINCT server-side you have to use Projections.Distinct .
You have to make an explicit subquery. Here there are two variants of the query. the first one is more similar to the LINQ query, the second one doesn't use the Count but uses the Exist (in LINQ you could have done the same by changing the Count(...) > 0 with a Any(...)
Note that when you use a .Select() you normally have to explicitly tell the NHibernate the type of the .List<something>()
Events x = null;
Receivers t = null;
// Similar to LINQ, with COUNT
var subquery2 = QueryOver.Of<Receivers>(() => t)
.Where(() => t.SOMETHING == x.SOMETHING) // The JOIN clause between Receivers and Events
.ToRowCountQuery();
var result2 = Session.QueryOver<Events>(() => x)
.Where(Restrictions.Disjunction()
.Add(() => x.Owner.ID == 1)
.Add(() => x.EVType.ID == 123)
.Add(Subqueries.WhereValue(0).Lt(subquery2))
)
.Select(Projections.Distinct(Projections.Property(() => x.StartDate)))
.List<DateTime>();
// With EXIST
var subquery = QueryOver.Of<Receivers>(() => t)
.Where(() => t.SOMETHING == x.SOMETHING) // The JOIN clause between Receivers and Events
.Select(t1 => t1.ID);
var result = Session.QueryOver<Events>(() => x)
.Where(Restrictions.Disjunction()
.Add(() => x.Owner.ID == 1)
.Add(() => x.EVType.ID == 123)
.Add(Subqueries.WhereExists(subquery))
)
.Select(Projections.Distinct(Projections.Property(() => x.StartDate)))
.List<DateTime>();
Note that you'll have to set "manually" the JOIN condition in the subquery.
Hopefully this answer can help others. This error was being caused by declaring
List<Receivers> t = null;
followed by the query expression
t.Count(y => y.User.ID == 1) > 0
The QueryOver documentation states "The variable can be declared anywhere (but should be empty/default at runtime)." Since in this case, the place holder is a List, you must initialize it as an empty list.
List<Receivers> t = new List<Receivers>();
Otherwise, when you try to reference the Count method, or any other method on the placeholder object, the source (t) will be null.
This however still leaves a problem as #fex and #xanatos, in which it makes no sense to reference Count() from the alias List t, as it won't convert into SQL. Instead you should be creating a subquery. See their answers for more comprehensive answer.
Query 1
var resulty = db.QIS
.Where(w=>w.QSA.Any(a => a.QSID != w.QSID))
.Select(s => s.QSID).ToList();
Query 2
var resultz = db.QIS
.Where(w=>w.QSA.Where(h => h.QSID == w.QSID).Select(s => s.QSID).FirstOrDefault() != w.QSID)
.Select(s => s.QSID).ToList();
Table QIS and QSA are related Many:Many. The idea here is to find how many QIS.ID's are not Found in QSA where QIS.QID == QSA.QID.
Query 1 returns 0
Query 2 on the other hand gives me what I expected to see ( the list off all non matching QIS records.)
Why will the any not work? - i found myself running into the same situation a couple of times now in seperate scenarios... thanks for any help / thoughts.
PS: Prefer method syntax.
In the filtering in your second version, will only be true if the inner Where clause returns no elements, so that FirstOrDefault() returns null or 0 (depending on if the type is nullable or not).
w=>w.QSA.Where(h => h.QSID == w.QSID)
.Select(s => s.QSID).FirstOrDefault() != w.QSID
Which is equivalent to (now assuming QSID is a non nullable numeric type, if it is nullable, use null instead of zero):
w=>w.QSA.Where(h => h.QSID == w.QSID)
.Select(s => s.QSID).FirstOrDefault() == 0
which can be rewritten to:
w=>w.QSA.Where(h => h.QSID == w.QSID).FirstOrDefault() == null
which can be rewritten to:
w=>!w.QSA.Any(h => h.QSID == w.QSID)
which is nearly the same as your initial version, but not exactly. You still want to check for equivalence inside the Any() filter, but then negate the result.